Abstract

The seismic facies, facies architecture, and stratigraphy of tidal-inlet and tidal-delta deposits and their relation to the development of adjacent coastal lithosomes are examined using high-resolution seismic profiles, vibracores, and borehole descriptions. The Bolivar Roads tidal inlet/delta complex, along the east Texas Gulf coast, was formed nearly equal 3.3 ka by spit accretion across a baymouth following a rapid sea-level rise nearly equal 4 ka. An increase in the tidal prism through time and entrenchment of the tidal inlet over the Trinity River incised valley stabilized the inlet and intensified tidal processes on the tidal inlet/delta complex. The tidal-inlet facies show channel stacking and cut-and-fill structures. Stacked clinoforms dip westward across the inlet. The spit facies is characterized by oblique-tangential clinoforms that build outward and deepen from the edge toward the center of the valley. The flood-tidal delta facies has a base that shallows abruptly bayward. As the flood-tidal delta facies thins bayward, it interfingers with bay sediments. Near the inlet the flood-tidal delta shows channel cut-and-fill with an overall channel stacking pattern. On the seaward side the channels have a trough-like geometry. Bayward, the channels broaden and shallow. The channels show a prograded-fill pattern. The ebb-tidal delta facies exhibits gently inclined clinoforms prograding over a ravinement surface. Tidal-inlet deposits are composed of sand, shell, and mud interbeds. Sand and clay interlaminae are ubiquitous in the tidal deltas, and sand and shell beds are common near the inlet. Overall, the Bolivar Roads tidal inlet/delta complex is mud-dominated as a result of high influx of fine sediment into the bay.

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